Such .[.Ser. No. 121,842 application.]. .Iadd.patent .Iaddend.discloses apparatus capable of utilizing a reference signal inserted in the vertical blanking interval of a transmitted television waveform to improve the consistency of reproduced color. As is therein described, tighter control of the phase of the sub-carrier oscillator of the receiver (with a resulting improvement in color demodulation) is attained by employing the transmitted color synchronizing burst signal to lock the oscillator in frequency and by additionally employing the transmitted reference signal to lock it in phase. This use of the periodically recurring burst to independently control oscillator frequency was noted as being advantageous in that it enabled the apparatus to have a speed of response and a signal-to-noise ratio comparable to those exhibited by typical NTSC frequency and phase control arrangements. There the burst signal alone is employed to set the oscillator as the reference against which the demodulation occurs.
Because the reference signal was of much longer duration than the synchronizing burst, however, its use in controlling the phase of the oscillator proved advantageous as it was substantially less subject to phase variations from such phenomena an multipath and transmission line reflection, for example. Use of the color reference signal instead of the synchronizing burst as the measure in providing automatic chroma control for saturation correction was similarly noted as being superior in that the amplitude of the reference signal was not subject to the cumulative tolerances associated with the burst signal amplitude.